Comparing PSMA PET/CT and MRI-RSI for Finding and Outlining Tumors Inside the Prostate in Men With Newly Diagnosed Prostate Cancer

Prospective Comparison of PSMA PET/CT and MRI-RSI (Restriction Spectrum Imaging) for Intraprostatic Tumor Detection and Delineation in Primary Prostate Cancer Patients

The detection and delineation of the intraprostatic tumor burden plays a crucial role in the personalized treatment of primary prostate cancer. The current gold standard multiparametric magnetic resonance imaging (mpMRI) is used to guide targeted prostate biopsies for initial diagnostic work up and for definitive focal dose-escalated radiotherapy in intermediate and high-risk prostate cancer patients.

However, mpMRI might underestimate the tumor volume and manual gross tumor volume delineation based on mpMRI underlies significant interobserver variability. Thus, novel imaging modalities are warranted to increase the detection rate and/or decrease the interobserver variability during tumor delineation.

This study will prospectively compare two promising advanced medical imaging methods: MRI-RSI and PSMA PET with the current gold-standard mpMRI for tumor detection and delineation in primary prostate cancer patients.

Inclusion Criteria:

• Newly diagnosed and histologically confirmed primary prostate cancer
• NCCNv4.2024 risk groups: unfavorable intermediate risk, high-risk and very high-risk
• Males, age ≥ 18 years
• ECOG performance status 0-2
• Estimated life expectancy ≥ 5 years
• PSMA-PET/CT-hybrid imaging performed <3 months
• MRI-targeted biopsy on PIRADs v2.1 lesion ≥3 performed <6 months

Exclusion Criteria:

• Contraindications for MRI imaging
• No visible tumor on PSMA PET and mpMRI (defined by PIRADs v2.1 ≤2 lesion)
• TUR-P of the prostate <1 year ago
• Initial PSA >100 ng/ml
• History of cancer (exception: localized skin tumours, tumours treated ≥5 years previously with curative intent and no evidence of recurrent disease)
• Previous radiation therapy to the pelvis
• ADT or ADT + other systemic therapy before inclusion